我如何在Swift中显示一条弹出消息，该消息在3秒钟后消失，或者可以被用户立即取消

Question

在我的swift应用程序中，我有一个带有单个按钮的UIViewController。

此按钮调用一个函数，该函数调用3秒钟后消失的弹出窗口。此外，在那之后，它会向控制台打印一条消息。此功能的代码如下：

func showAlertMsg(title: String, message: String){

    let alertController = UIAlertController(title: title, message: message, preferredStyle: .Alert)
    self.presentViewController(alertController, animated: true, completion: nil)
    let delay = 3.0 * Double(NSEC_PER_SEC)
    let time = dispatch_time(DISPATCH_TIME_NOW, Int64(delay))
    dispatch_after(time, dispatch_get_main_queue(), {
        alertController.dismissViewControllerAnimated(true, completion: nil)
    print("popup disappeared")
    })
}

这很好，但我想介绍一些改进。我想添加一个按钮，可以立即取消弹出窗口，然后避免在控制台中显示消息。有没有办法向用户显示这样的弹出窗口？此外，有没有一种方法可以在弹出消息中显示计数器的秒数，显示弹出消息消失前还有多少时间？

Answer 1

您可以使用NSTimer递减计数器，更新警报视图，并在计数器达到0时关闭警报视图。此代码改编自我的Objective-C答案

class ViewController: UIViewController {
    var alertController: UIAlertController?
    var alertTimer: NSTimer?
    var remainingTime = 0
    var baseMessage: String?
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
    }
    override func viewDidAppear(animated: Bool) {
        super.viewDidAppear(animated)         
        self.showAlertMsg("Test Alert", message: "This will disappear in ", time: 5)
    }
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
    func showAlertMsg(title: String, message: String, time: Int) {
        guard (self.alertController == nil) else {
            print("Alert already displayed")
            return
        }
        self.baseMessage = message
        self.remainingTime = time
        self.alertController = UIAlertController(title: title, message: self.alertMessage(), preferredStyle: .Alert)
        let cancelAction = UIAlertAction(title: "Cancel", style: .Cancel) { (action) in
            print("Alert was cancelled")
            self.alertController=nil;
            self.alertTimer?.invalidate()
            self.alertTimer=nil
        }
        self.alertController!.addAction(cancelAction)
        self.alertTimer = NSTimer.scheduledTimerWithTimeInterval(1.0, target: self, selector: #selector(ViewController.countDown), userInfo: nil, repeats: true)       
        self.presentViewController(self.alertController!, animated: true, completion: nil)     
    }
    func countDown() {
        self.remainingTime -= 1
        if (self.remainingTime < 0) {
            self.alertTimer?.invalidate()
            self.alertTimer = nil
            self.alertController!.dismissViewControllerAnimated(true, completion: {
                self.alertController = nil
            })
        } else {
            self.alertController!.message = self.alertMessage()
        }
    }
    func alertMessage() -> String {
        var message=""
        if let baseMessage=self.baseMessage {
            message=baseMessage+" "
        }
        return(message+"(self.remainingTime)")
    }     
}

Answer 2

如果有人需要，这是@Paulw11解决方案的Swift 4版本

import UIKit
class ViewController: UIViewController {
    var alertController: UIAlertController?
    var alertTimer: Timer?
    var remainingTime = 0
    var baseMessage: String?
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
    }
    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        self.showAlertMsg(title: "Test Alert", message: "This will disappear in ", time: 5)
    }
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
    func showAlertMsg(title: String, message: String, time: Int) {
        guard (self.alertController == nil) else {
            print("Alert already displayed")
            return
        }
        self.baseMessage = message
        self.remainingTime = time
        self.alertController = UIAlertController(title: title, message: self.alertMessage(), preferredStyle: .alert)
        let cancelAction = UIAlertAction(title: "Cancel", style: .cancel) { (action) in
            print("Alert was cancelled")
            self.alertController=nil;
            self.alertTimer?.invalidate()
            self.alertTimer=nil
        }
        self.alertController!.addAction(cancelAction)
        self.alertTimer = Timer.scheduledTimer(timeInterval: 1.0, target: self, selector: #selector(ViewController.countDown), userInfo: nil, repeats: true)
        self.present(self.alertController!, animated: true, completion: nil)
    }
    @objc func countDown() {
        self.remainingTime -= 1
        if (self.remainingTime < 0) {
            self.alertTimer?.invalidate()
            self.alertTimer = nil
            self.alertController!.dismiss(animated: true, completion: {
                self.alertController = nil
            })
        } else {
            self.alertController!.message = self.alertMessage()
        }
    }
    func alertMessage() -> String {
        var message=""
        if let baseMessage=self.baseMessage {
            message=baseMessage+" "
        }
        return(message+"(self.remainingTime)")
    }
}

Answer 3

我知道这并不能直接回答您的问题，但您是否考虑过使用MBProgressHUD SCLAlertView？它们都提供了一些功能，允许您显示一个在一定时间后消失的警报。SCLAlertView允许用户在MBProgressHUD不允许的情况下立即取消。如果你想要更多关于如何实现这些的信息，请告诉我，这样我就可以添加更多信息！